These two never-used postcards were made prior to 1951, because they are pre-printed with one-cent postage. Postcard postage increased from one penny to two pennies on January 1, 1952. Most likely, the postcards are from much earlier, possibly as early as the 1920s.
They are advertising for Atlantic quality lubricants1 (motto: "Keep Upkeep Down"), touting the company's transmission oils for winter and "high film-strength motor oil".
At the bottom of the cards is printed:
BISIGNANI NASH MOTOR CO.
941 Main Street
Peckville is an unincorporated village within the borough of Blakely, Pennsylvania, in Lackawanna County.
The only online reference I found to Bisignani Nash Motor Co. is within an advertisement in the February 14, 1930, edition of the Republican Watchman2, a newspaper out of Monticello, N.Y. It's a testimonial for Gold Bound Anti Freeze from Duffy Bisignani.
I also found this image of an old sign from Bisignani Motor Co. on the LiveAuctioneers website.
1. Two other examples of postcards of this type can be viewed here and here. Other Atlantic postcards I came across have automotive companies in Huntingdon, Pa., and McGees Mills, Pa., printed on the bottom of the card.
2. Published from 1866 to 1971. See more details here.